This invention generally relates to a root-crop harvester. More particularly, this invention relates to an endless screening band for a root-crop harvester. Still more particularly, this invention relates to an endless screening band for a root-crop harvester of the type having two lateral belts which are connected to each other by means of crossrods permanently riveted to the outside of the belts and which on the inside have uniformly-spaced, inwardly-directed entrained cleats whose purpose is to engage entrainer disks which deflect into the screening band. Such a screening band is described, for example, in German Offenlegungsschrift No. 31 09 209 (which is embodied herein by reference).
FIG. 5 shows a root-crop harvester of the type disclosed in the aforementioned German Offenlegungsschrift No. 31 09 209. The root-crop harvester of FIG. 5 includes an endless screening band 19 having endless lateral belts 1 and a deflection roller 20 having entraining disks 21 on each end. As is shown in FIG. 5, ridges 22 on entrainer disks 21 engage cleats 14, 15, and 16 to thereby cause movement of screening band 19.
Endless circulating screening bands of this type are used especially in potato harvesters. They take the earth consisting of soil and potatos from the ground, screen out the soil and small stones included in it, and convey the potatoes together with the potato greens or haulm, into the harvester. Deflection rollers which are elastic in accordance with the aforementioned German Offenlegungsschrift No. 31 09 209 are used for the rearward deflection. The rear deflection roller has, on both sides, an entrainer disk which, with ridges, is capable of gripping between the entrained cleats of each belt, thereby entraining the screening band in a positive manner.
To be able to rivet the crossrods to the belts, the rivet holes must pass through the belts between two entrained cleats. Hence, the crossrods are located above the gaps between the entrained cleats or else above every second or multiple gap between the entrained cleats. In any case, the spacing of the crossrods can only correspond exactly to the spacing of the entrained cleats or to a multiple thereof.
Different harvesting conditions, caused particularly by especially moist or dry weather periods, make it necessary to replace the screening band by one having a crossrod spacing which no longer corresponds to the spacing of the entrained cleats. Then it becomes necessary also to replace the entrainer disks in addition to the screening band. This often requires quite a lot of work, since the entrainer disks usually have poor accessibility and may be difficult to detach owing to encrusted dirt or corrosion.
To obviate the need for this replacement of the entrainer disks, the cited German Offenlegungsschrift advocates using screening bands with belts that are flat on the inside, so that the drive force is transmitted solely by frictional engagement. This makes entrainer disks superfluous, so that a changing of the screening band can proceed more quickly, but it often happens that the screening band is not entrained by the driving roller or that a steady slip occurs between the screening band and the driving roller. Hence, the positive coupling between the screening band and the driving roller is not dispensed with in practice.